Polyester polyols are often used in the manufacture of urethane elastomers, coatings, adhesives, ink binders, and the like. In some cases, the polyols are used as mixtures to achieve a balance of properties. Many polyester and polyether polyols have melting temperatures above room temperature and usually must be heated to liquify them before use. The resulting polyurethane or polyurethane-containing article may be subject to outdoor conditions or wet environments, which can cause gradual hydrolysis and eventual failure of the polyurethane. Certain applications such as artificial leather and shock-absorber components must withstand repeated flexing without failure, sometimes at low temperatures.
In some cases, polyether polyols, which often impart better resistance to hydrolysis than polyester polyols, can be used instead of polyester polyols. However, polyester polyols or copolymers containing ester groups impart certain advantageous properties to polyurethanes which may be required for adequate performance in a given application, such as tear resistance, oil, hydrocarbon or solvent resistance, high temperature stability, adhesion, paintability, high tensile strength, vibrational damping properties, and the like.
Polycaprolactone polyols provide the additional advantages, relative to other aliphatic polyester polyols, of higher purity and consistency, longer pot life (in reactive formulations) and especially lower viscosity. They also can provide articles with the advantages of lower color, lower permanent set (elastomers), improved weatherability, and better hydrolytic stability.
However, despite the advantages of polycaprolactone polyols, in some applications improvements in low-temperature flexibility are required. Also desired are polyols which are liquid at or close to ambient temperature to render them more easily handled without heating. Although low-temperature flexibility properties can be improved by use of certain polyether polyols (e.g., polytetrahydrofuran type), such polyols suffer from oxidative instability which renders them unsuitable for certain applications where sustained exposure to hot conditions or ultraviolet light is expected.
U.S. Pat. No. 3,845,160 discloses polymers of trioxane with either ε-caprolactone or 1,3-dioxepane as a comonomer present in minor amount, but does not specifically disclose copolymers of ε-caprolactone and 1,3-dioxepane as the major components nor copolymers without trioxane as the major component.
British Patent 1,252,824 discloses an aqueous dispersion of a modified polyacetal prepared from a terpolymer of 93% trioxane with 5% 1,3-dioxepane and 2% propiolactone, but does not specify copolymers of other lactones, nor copolymers without trioxane as the major component.
Japanese Patent 03126751 A2 discloses blends of aliphatic polyesters including polycaprolactone in copolymers of trioxane and 1,3-dioxepane for the purposes of improving the crystallization rate and heat resistance of subsequent compositions.
All of these prior art disclosures are directed toward improved poly(1,3,5-trioxane) polymers, and utilize 1,3-dioxepane and lactones and their polymers only as modifiers, not as the main constituents of the compositions.